Tuesday Night Weather Blog: Subfreezing Temperatures Coming

An arctic surge is going to kick off this brand new year, but the forecast is not as clear cut as one might think.

The first cold front passed us on Sunday evening and that ushered in modestly cooler weather on New Years Eve and New Years Day. A second and somewhat ill-defined cold front extending from the Tennessee and Georgia mountains to near the Arklatex is going to blend in with the first front, sending us the arctic blast. A strong pressure gradient between a high over the High Plains and a low near Cape Cod will keep the wind blowing from the northwest between 8 and 15 mph tonight into Wednesday morning. The statistical models are forecasting lows between 24 and 26 degrees, but the direct gridded data from the same models are showing between 28 and 32 degrees. When the wind is blowing (especially over 5 mph), the air near the ground has a tough time cooling down to its greatest potential because of molecular mixing and compression. As a result, I am forecasting the low temperature to bottom out at 29 degrees, give or take 3 degrees depending upon your location. That means we will see a light to moderate freeze at most locations, including the coast. The National Weather Service has issued a hard freeze warning tonight, but the temperature must drop to 25 degrees or colder for at least 2 consecutive hours for the definition of a hard freeze to be met. Since I do not believe we will get that cold for that long, I am not advertising a hard freeze Wednesday morning in my broadcasts. I just wanted to clear up any possible confusion. The wind chill should get between 18 and 20 degrees by sunrise.

Wednesday will be an exceptionally cold day with a northwest wind sustained between 15 and 25 mph. Gusts could exceed 30 mph in places. The thermometer should only peak in the low to mid 40s, but the wind chill will be in the 30s most of the day.

The toughest part of the forecast is Wednesday night and Thursday morning. The center of high pressure is expected to reach middle Tennessee. That's far away and that argues against the wind going calm all night long, except for brief periods here and there. The statistical model guidance is predicting a devastating freeze not seen here in more than a decade. The GFS model is showing 13 degrees, Eta 15 degrees, and NGM 19 degrees. I believe these models to be in error. As of one my professors said at FSU, it's tough to get an epic freeze in this area when the center of high pressure is north of Dallas' latitude. Tennessee is north of Dallas. That said, I do believe we will see our first hard freeze of the season. I am forecasting a low temperature of 24 degrees on average across our area. Some out-of-town locales will almost certainly dip into the lower 20s and it's not entirely out of the question that the very coldest locations will slip below 20. However, I do not expect teens to be a widespread occurrence over our viewing area. Still, pipes can freeze when the temperature dips below 25 degrees for several hours and we do urge everyone to take the necessary precautions. We will continue to carefully monitor the situation and if the high gets farther south (resulting in a calm wind for longer than we currently anticipate), then we'll adjust the temperature forecast a little lower. The bottom line is that we do expect a hard freeze, but not a historic one as some of the stastical models indicate.

As the arctic high pressure moves toward the Atlantic coast, our airmass will gradually modify and the winds will turn more toward the east and southeast. We could manage to see another light freeze late Thursday night into Friday morning, but then morning lows should stay above freezing this upcoming weekend. Highs will get back into the 50s Friday, into the 60s Saturday, then back close to 70 degrees on Sunday. That will sure feel nice after what we're about to endure!

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